Solenoid having fluid accumulating and plunger chambers

ABSTRACT

A solenoid improvement has been achieved in terms of abrasion resistance. A fluid accumulating chamber Q is formed substantially coaxially with a plunger chamber P and on the opposite side of a center post  4  through the intermediation of the plunger chamber P. On the outer peripheral side of the rod  6 , there is provided a first bearing  7  for separating the plunger chamber P and the fluid accumulating chamber Q from each other.

This is a nationalization of PCT/JP01/01494 filed Feb. 28, 2001 andpublished in Japanese.

TECHNICAL FIELD

This invention relates to a solenoid that is suitable for use in asolenoid valve or the like to be used in controlling, for example,various types of hydraulic and pneumatic apparatuses.

BACKGROUND ART

FIG. 11 shows an example of a conventional solenoid of this type. FIG.11 is a schematic sectional view of a conventional solenoid.

This solenoid 100 is used as the driving means of a control valve, suchas a spool valve for controlling, for example, hydraulic pressure. It ismounted in a liquid-tight fashion in a housing 200 filled with oilserving as the fluid through the intermediation of an O-ring 201. Thatis, a valve or the like (not shown) is mounted to the forward end of arod 106 constituting the solenoid 200, and is driven in a state in whichit is immersed in an oil (O) to thereby perform hydraulic pressurecontrol or the like.

This solenoid 100 comprises a plunger 103 made of a magnetic materialand slidably inserted into a bearing 102 provided in a plunger chamber Pformed inside a hollow solenoid main body 101, a center post 104 formedof a magnetic material and arranged opposite to and coaxially with theplunger 103, a cap 105 which is provided on the opposite side of thecenter post 104 to regulate axial movement of the plunger 103 and whichcloses the plunger chamber P, and a rod 106 connected to the plunger103.

The rod 106 is inserted and secured in a through-hole 103 a extendingalong the center axis line of the plunger 103, and extends on the centerpost 104 side. Further, the center post 104 also has a through-hole 104a extending along the center axis line thereof, and the rod 106 isinserted into this through-hole 104 a through the intermediation of abearing so as to be capable of reciprocating such that its forward endportion protrudes outwardly.

And, as stated above, a valve or the like (not shown) is connected tothe forward end of this rod 106, and is operated in accordance with themovement of the rod 106.

In this solenoid 100, normally, that is, when the solenoid main body 101is not being energized, the plunger 103 is moved to the cap 105 sidethrough the rod 106 due to the pressure of the external fluid such asoil or the force of a spring for returning the rod 106 in the valve orthe like.

And, when the solenoid main body 101 is being energized, the plunger 103is magnetically attracted to the center post 104, whereby the rod 106connected to the plunger 103 moves to the left in the drawing to therebydrive the valve or the like.

Since the solenoid 100 is mounted in oil in a liquid-tight fashion, theoil may offer resistance when operating the plunger 103, therebyaffecting the responsiveness of the plunger.

In order that the responsiveness of the plunger 103 may not be affected,there are provided oil holes 104 b and 103 b extending axially throughthe center post 104 and the plunger 103, respectively, whereby the oilfrom the exterior (P0) of the solenoid 100 flows through the oil hole104 b, the portion (P1) between the center post 104 and the plunger 103,and the oil hole 103 b to the portion (P2) between the plunger 103 andthe cap 105.

That is, in this case, the external oil moves as follows: P0→P1 andP1→P2 due to the movement of the plunger 103 (See the arrows in thedrawing).

Although this construction helps to achieve an improvement inresponsiveness, there still remains a problem in terms of durability dueto abrasion or the like.

That is, as a result of wear of the valve or the like, a large amount ofcontaminants exist in the oil.

In particular, in the case where the flow passage as described above isformed, contaminants are likely to gather in the portion (P1) betweenthe center post 104 and the plunger 103. This is because this portionconstitutes a part of a magnetic path and is magnetized.

Thus, when the contaminants accumulated in this portion enter theportion where the plunger 103 slides, the plunger 103 is further worn,and the control characteristics can be adversely affected.

In view of this, the present applicant has filed a patent applicationregarding a technique to solve the above problem. This technique isdisclosed in Japanese Patent Application Laid-Open No. Hei 9-89145.

This technique will be described with reference to FIG. 12. FIG. 12 is aschematic sectional view of a conventional solenoid.

As shown in FIG. 12, in this solenoid, the rod 206 is equipped with athrough-hole 206 a for directly guiding the external fluid (oil) to theplunger chamber P.

Due to this construction, the external fluid flows from the exterior(Q0) of the solenoid through the through-hole 206 a, the plunger chamberP (Q1), and an oil hole provided in the plunger to the portion (Q2)between the center post and the plunger.

Thus, the contaminants do not easily reach the portion (Q2) between thecenter post and the plunger, thus solving the above problem.

However, the above-described prior-art technique involves the followingproblem:

It is true that, by providing a through-hole serving as a flow passagein the rod, it is possible to some degree to achieve an improvement inabrasion resistance. However, it can happen that some of thecontaminants contained in the fluid directly guided to the plungerchamber get into the plunger sliding portion, resulting in adeterioration in abrasion resistance.

Thus, to further stabilize and improve the control characteristics,there is a demand for a further improvement in abrasion resistance.

Therefore, the present invention has been made with a view towardsolving the above problem in the conventional art. It is an object ofthe present invention to provide a high-quality solenoid in which animprovement has been achieved in abrasion resistance.

DISCLOSURE OF THE INVENTION

In accordance with the present invention, there is provided a solenoid,characterized in that the solenoid includes:

excitation means provided in a solenoid main body and excited throughenergization;

a center post secured in position inside the solenoid main body;

a plunger slidably provided in a bearing portion in a plunger chamberdefined in the solenoid main body and adapted to be attracted to thecenter post by a magnetic force through excitation of the excitationmeans;

a fluid accumulating chamber provided substantially coaxially with theplunger chamber and on the opposite side of the center post through theintermediation of the plunger chamber; and

a rod which is fixed to the inner periphery of a through-hole formed inthe plunger, one end of which protrudes so as to reach the fluid outsidethe solenoid main body through a through-hole formed in the center post,and the other end of which protrudes so as to reach the interior of thefluid accumulating chamber, and

that the rod has a through-hole for guiding the fluid outside thesolenoid main body to the interior of the fluid accumulating chamber,and

that a first cutoff portion separating the plunger chamber and the fluidaccumulating chamber from each other is provided on the outer peripheralside of the rod.

Thus, when the plunger operates, outside fluid is guided to the fluidaccumulating chamber through the through-hole formed in the rod, so thatthe operation of the plunger is not hindered by the pressure of theoutside fluid. Thus, the solenoid is superior in responsiveness.Further, since the fluid guided to the fluid accumulating chamber isintercepted by the first cutoff portion, it does not directly enter theplunger chamber, and even if the fluid contains contaminants, it ispossible to prevent the contaminants from entering the plunger slidingportion.

The first cutoff portion consists of an annular member, and the innerperiphery of the annular member is caused to slide on the outerperiphery of the rod, and, further, the outer periphery of the annularmember is brought into close contact with the inner peripheral portionof the fluid accumulating portion, whereby the plunger chamber and thefluid accumulating chamber are separated from each other.

Due to this construction, it is possible to reduce the possibility ofcontaminants contained in the fluid entering the sliding portion betweenthe inner periphery of the annular member and the outer periphery of therod as compared with the possibility of contaminants contained in thefluid entering the sliding portion in the outer periphery of the plungerin the conventional structure in which the fluid is directly guided tothe plunger chamber. That is, generally speaking, the dimensional errorinvolved is larger and the gap can be so much the larger when somethingwith a large diameter is supported by a bearing than when something witha small diameter is supported by a bearing.

It is desirable for the sliding portion between the inner periphery ofthe annular member and the outer periphery of the rod to be positionedoutside the magnetic path formed when the excitation means is excited.

This makes it possible to prevent magnetic contaminants from beingattracted to the sliding portion by magnetic force.

It is desirable to provide on the outer peripheral side of the rod asecond cutoff portion separating the plunger chamber and the exterior ofthe solenoid main body from each other.

Thus, no fluid directly enters the plunger chamber from the exterior ofthe solenoid main body, further making it possible to preventcontaminants from entering the plunger sliding portion.

It is desirable for at least one of the first and second cutoff portionsto be the bearing of the rod.

It is also desirable for at least one of the first and second cutoffportions to be a seal member sealing the outer periphery of the rod.

It is desirable to provide a filter in the through-hole formed in therod.

Thus, it is possible to prevent contaminants or the like from enteringthe fluid accumulating chamber.

It is desirable to provide at the end of the rod on the fluidaccumulating chamber side an elastic partition separating the fluidaccumulating chamber and the interior of the through-hole from eachother.

This helps to prevent intrusion of contaminants or the like into thefluid accumulating chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a solenoid according to a firstembodiment of the present invention;

FIG. 2 is a schematic sectional view of a modification of a solenoidaccording to the first embodiment of the present invention;

FIG. 3 is a schematic sectional view of a solenoid according to a secondembodiment of the present invention;

FIG. 4 is a schematic sectional view of a solenoid according to a thirdembodiment of the present invention;

FIG. 5 is a schematic sectional view of a solenoid according to a fourthembodiment of the present invention;

FIG. 6 is a schematic sectional view of a solenoid according to thefourth embodiment of the present invention;

FIG. 7 is a schematic sectional view of a solenoid according to thefourth embodiment of the present invention;

FIG. 8 is a schematic sectional view of a solenoid according to a fifthembodiment of the present invention;

FIG. 9 is a schematic sectional view of a solenoid according to a sixthembodiment of the present invention;

FIG. 10 is a schematic diagram showing a plunger constituting a solenoidaccording to a seventh embodiment of the present invention;

FIG. 11 is a schematic sectional view of a conventional solenoid; and

FIG. 12 is a schematic sectional view of a conventional solenoid.

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment)

A solenoid according to the first embodiment of the present inventionwill be described with reference to FIG. 1. FIG. 1 is a schematicsectional view of a solenoid according to the first embodiment of thepresent invention.

In FIG. 1, numeral 1 indicates the solenoid as a whole. This solenoid 1is suitably used to drive, for example, a control valve (such as a spoolvalve for controlling hydraulic pressure or the like).

When thus using the solenoid 1 for hydraulic pressure control, thesolenoid 1 is mounted in a liquid-tight fashion in a housing 50 filledwith oil serving as the fluid through the intermediation of an O-ring51. And a spool valve or the like (not shown) is mounted to the forwardend of a rod 6 that is one of the components of the solenoid 1, and thisspool valve or the like is driven by the solenoid 1 in a state in whichit is immersed in the oil (O) to thereby effect hydraulic pressurecontrol.

The solenoid 1 substantially comprises a hollow solenoid main body 2, aplunger 3 of a magnetic material slidably inserted into inner walls P1and P2 (functioning as bearing portions) of a plunger chamber P formedinside the solenoid main body, a center post 4 of a magnetic materialprovided opposite to and coaxially with the plunger 3, a cap 5 providedon the opposite side of the center post 4 and adapted to close theplunger chamber P, and a rod 6 connected to the plunger 3.

Here, the solenoid main body 2 is equipped with a case 8 open at bothends, a coil 10 serving as an excitation means wound around a bobbin 9which is accommodated in the case 8 and has a hollow portion, an upperplate 11 and a lower plate 12 serving as a magnetic path guide memberprovided at the upper and lower ends of the coil 10 through theintermediation of the bobbin 9, a lead wire 13 for energizing the coil10, etc.

The upper plate 11 is an annular member for guiding the magnetic pathfrom the center post 4 to the case 8, and is mounted such that its outerperipheral portion is in close contact with the portion near the openend of the case 8.

The lower plate 12 is an annular member for guiding the magnetic pathfrom the case 8 to the plunger 3 through a sleeve 14, and is embedded onthe opposite side of the upper plate 11 through the intermediation ofthe bobbin 9.

In the vicinity of the end portion of the bobbin 9 on the lower plate 12side, there is provided a terminal or the like for electricallyconnecting the lead wire 13 and the coil 10, and the coil 10 isenergized by an external power source (not shown) for excitation.

In the hollow portion of the bobbin 9, there is provided the sleeve 14of a magnetic material, and in the inner periphery of this sleeve 14,one end portion of the cap 5 extends to form a part of the inner wall(inner wall P1) of the plunger chamber P. Similarly, one end portion ofthe center post 4 extends to form a part of the inner wall (inner wallP2) of the plunger chamber P. The inner walls P1 and P2 also function asbearing portions, and the plunger 3 is slidably inserted with respect tothe inner walls P1 and P2.

As shown in FIG. 2, it is also possible to provide a sleeve B of anon-magnetic material on the inner side of the inner walls P1 and P2 andto use it as the bearing for the plunger 3. By thus forming the bearingby a single member, it is possible to slide the plunger 3 more smoothly.

Further, by the annular portion formed by extending one end portion ofthe above-mentioned cap 5, not only is a part of the plunger chamber Pformed, but also a fluid accumulating chamber Q is formed substantiallycoaxially with the plunger chamber P and on the opposite side of thecenter post 4 through the intermediation of the plunger chamber P.

The inner diameter of the fluid accumulating chamber Q is smaller thanthe inner diameter of the plunger chamber P.

The plunger 3 has a through-hole 31 extending along the center axisthereof, and a rod 6 is inserted and secured in the through-hole 31 byforcing-in or the like.

One end portion 6 a of this rod 6 extends on the center post 4 sidethrough a through-hole 41 formed in the center post 4 to the exterior ofthe solenoid main body 2, reaching the fluid in the exterior.

The other end portion 6 b of the rod 6 protrudes so as to reach thefluid accumulating chamber Q.

And the rod 6 has a through-hole 61 extending along the center axisthereof, and this through-hole 61 forms a flow passage for guiding theexternal fluid into the fluid accumulating chamber Q.

Further, a valve or the like (not shown) is connected to the forward endof the rod 6, and this valve or the like is operated in accordance withthe movement of the rod 6.

And, on the outer peripheral side of the rod 6, there is provided afirst bearing 7 serving as a first cutoff member for separating theplunger chamber P and the fluid accumulating chamber Q from each other.This first bearing 7 is an annular member, in the inner periphery ofwhich the outer periphery of the rod 6 is slidably inserted, its outerperiphery being in close contact with and secured to the inner peripheryof the fluid accumulating chamber Q.

The diameter of the outer periphery of the first bearing 7 is smallerthan the outer diameter of the plunger 3. Further, this first bearing 7also functions as the bearing of the rod 6.

Further, the plunger 3 has a through-hole 32 allowing the fluid at theaxial ends of the plunger 3 to flow.

Next, the operation, etc. of the solenoid 1, constructed as describedabove, will be described.

In this solenoid 1, in the normal state, that is, when the coil 10 isnot being energized, the plunger 3 is caused to move to the cap 5 sidethrough the rod 6 due to the pressure of the fluid such as hydraulicpressure of external control oil or the resilient force of a returnspring (not shown) for the rod 6 provided in the valve or the like.

When the coil 10 is energized through the lead wire 13, the coil 10 isexcited to form the magnetic path: the center post 4→the upper plate11→the case 8→the lower plate 12→the sleeve 14→the plunger 3→the centerpost 4 (indicated by the arrow J; however, the drawing only shows a partof the magnetic path, and it goes without saying that the magnetic pathis formed in the entire circumference) to thereby form a magneticcircuit.

As a result, a thrust due to a magnetic force is generated between theopposing surfaces of the plunger 3 and the center post 4, and theplunger 3 is magnetically attracted toward the center post 4, wherebythe rod 6 connected to the plunger 3 also moves. Of course, the valve orthe like mounted to the forward end of the rod 6 also moves.

Since the solenoid 1 is mounted liquid-tight to fluid, it is to beexpected that when the plunger 3 operates, the fluid (usually consistingof oil) offers resistance to affect the responsiveness of the plunger.However, in the construction of this embodiment, the through-hole 61 isformed in the rod 6 to secure the flow passage, so that theresponsiveness of the plunger 3 is not affected.

Further, in this embodiment, the through-hole 32 is provided in theplunger 3, so that the influence on the responsiveness is so much theless.

When the plunger 3 is driven, the external fluid flows between theexterior and the fluid accumulating chamber Q through the through-hole61 provided in the rod 6. However, due to the provision of the firstbearing 7, it does not directly flow into the plunger chamber P. Thatis, the external fluid flows between the portions R0 and R1 in thedrawing.

Thus, even if the fluid contains contaminants, it is possible to preventthe contaminants from getting between the plunger 3 and the center post4 and into the sliding surface of the plunger 3, so that it is possibleto achieve an improvement in the abrasion resistance of the plunger 3and an improvement in durability.

Thus, when the solenoid is used as a control valve, it is possible tostabilize and improve the control characteristics.

Further, as stated above, since sliding is effected between the innerperiphery of the first bearing 7 and the outer periphery of the rod 6,the possibility of contaminants entering the sliding portion between thefirst bearing 7 and the outer periphery of the rod 6 can be lower thanthe possibility of contaminants contained in the fluid entering thesliding portion in the outer periphery of the plunger in theconventional construction in which the fluid is directly guided to theplunger chamber, which further contributes to achieving an improvementin abrasion resistance.

This is due to the fact that, generally speaking, the dimensional errorinvolved is larger when something with a large diameter is supported bya bearing than when something with a small diameter is supported by abearing, and that it is highly possible that the gap is so much thelarger.

This problem cannot be solved by simply diminishing the plungerdiameter. For, in the case of a plunger, it is necessary to meetlimitation in dimension, etc. to some degree in order that the solenoidcan function as such (by securing a sufficient magnetic path, etc.)

Further, by positioning the sliding portion between the first bearing 7and the outer periphery of the rod 6 outside the magnetic path, it ispossible to prevent magnetic contaminants from being attracted to thissliding portion, thereby further contributing to an improvement inabrasion resistance.

That is, some contaminants are magnetic, and can be attracted to andcollected in a place where a magnetic path is formed. In thisembodiment, a part of the flow passage or the sliding portion situatedin the vicinity thereof is spaced apart from the magnetic path, wherebythe above problem can be eliminated.

While in the above-described example the inner walls for forming theplunger chamber P, functioning as the bearing of the plunger 3, areformed by a part of the cap 5 (the inner wall P1) and a part of thecenter post 4 (the inner wall P2), the inner wall should not, of course,be restricted to be constructed in such a way.

(Second Embodiment)

In the second embodiment shown, for example, in FIG. 3, it is possibleto form the above-mentioned inner walls by a part of the cap 5 (theinner wall P1) and an inner wall P3 formed by extending one end portionof the upper plate 11.

(Third Embodiment)

FIG. 4 is a schematic sectional view of a solenoid according to thethird embodiment.

In the example shown in FIG. 4, of the bearings of the rod 6, the secondbearing 71 on the oil (O) side is utilized as a cutoff member (secondcutoff member) for separating the exterior of the solenoid main body 2and the plunger chamber P from each other, whereby it is possible toprevent external fluid from directly flowing into the plunger chamber P.

Thus, even if the fluid contains contaminants, it is possible to preventthe contaminants from getting between the plunger 3 and the center post4 and into the sliding surface of the plunger 3, so that it is possibleto achieve an improvement in the abrasion resistance of the plunger 3and an improvement in durability.

(Fourth Embodiment)

While in the above-described embodiment a bearing is used as the cutoffmember, anything will do as long as it can effect separation. It is alsopossible to use a dedicated seal member.

Such cases will be described with reference to FIGS. 5 through 7. FIGS.5 through 7 are schematic sectional views of solenoids according to thefourth embodiment of the present invention.

It goes without saying that the same effect can be obtained when, forexample, as shown in FIG. 5, mounting grooves are respectively providedin the center post 4 and the first bearing 7, and O-rings 7 a and 7 bserving as seal members are provided therein.

The same effect can also be obtained when, as shown in FIG. 6, theO-ring 7 b is provided only on the center post 4 side, or when, as shownin FIG. 7, the O-ring 7 a is provided only in the first bearing 7.

(Fifth Embodiment)

FIG. 8 is a schematic sectional view of a solenoid according to thefifth embodiment of the present invention.

In this embodiment, a filter 15 is provided in the through-hole 61formed in the rod 6.

Due to the provision of the filter 15, it is possible to interceptcontaminants or the like contained in the fluid, so that it is possibleto prevent contaminants or the like from entering the fluid accumulatingchamber Q.

Thus, it is possible to further improve the abrasion resistance of theplunger 3, making it possible to achieve an improvement in terms ofdurability.

In the structures of the above-described embodiments, contaminants arehard to discharge from the fluid accumulating chamber Q once they haveentered it, whereas, in this embodiment, it is possible to preventcontaminants from entering the fluid accumulating chamber, which proveseffective.

While the example shown in FIG. 8 is applied to the type of structureshown in FIG. 5 referred to in the description of the fourth embodiment,an application of this embodiment is not limited to such a case. It canalso be applied to the types of structure shown in FIGS. 1 through 5 and7.

(Sixth Embodiment)

FIG. 9 is a schematic sectional view of a solenoid according to thesixth embodiment of the present invention.

In this embodiment, at the end of the rod 6 on the fluid accumulatingchamber Q side, there is provided a diaphragm 16 serving as an elasticpartition separating the fluid accumulating chamber Q and the interiorof the through-hole 61 from each other.

Due to the provision of the diaphragm 16, it is possible to interceptcontaminants or the like contained in the fluid, so that it is possibleto prevent contaminants or the like from entering the fluid accumulatingchamber Q.

Thus, it is possible to further improve the abrasion resistance of theplunger 3, making it possible to achieve an improvement in terms ofdurability.

Further, when fluid flows into the through-hole 32 as a result of thereciprocation of the plunger 3, the diaphragm 16 is deformed inaccordance with the amount of fluid flowing in to vary the fluidaccommodation volume, so that the plunger operation is not hindered bythe pressure of the external fluid, and a satisfactory responsiveness isachieved.

While in the example shown in FIG. 9 this embodiment is applied to thetype of structure shown in FIG. 6 referred to in the description of thefourth embodiment, an application of this embodiment is not limited tosuch a case. It can also be applied to the types of structure shown inFIGS. 1 through 5 and 7.

(Seventh Embodiment)

FIG. 10 is a schematic diagram showing a plunger constituting a solenoidaccording to the seventh embodiment of the present invention (FIG. 10Ais a plan view and FIG. 10B is a sectional view).

While in the examples referred to in the description of the aboveembodiments the through-hole 32 provided in the plunger 3 constitutesthe flow passage formed in the plunger 3, it is also possible, as shownin FIG. 10, to provide a slit 33 and to use it as the flow passage.

INDUSTRIAL APPLICABILITY

As described above, in the present invention, the rod has a through-holefor guiding the fluid outside the solenoid main body to the interior ofthe fluid accumulating chamber, whereby a superior responsiveness isachieved. Further, on the outer peripheral side of the rod, there isprovided a first cutoff portion for separating the plunger chamber andthe fluid accumulating chamber from each other, so that it is possibleto prevent fluid from directly entering the plunger chamber, making itpossible to prevent contaminants from entering the plunger slidingportion, whereby an improvement in abrasion resistance is achieved and asuperior quality is obtained.

When the cutoff portion consists of an annular member, and its innerperiphery is caused to slide on the rod outer periphery, it is possibleto reduce the possibility of contaminants entering the sliding portion.

When the portion where the inner periphery of the annular member slideson the rod outer periphery is positioned outside the magnetic path, itis possible to prevent magnetic contaminants from being attracted to thesliding portion by a magnetic force.

On the outer peripheral side of the rod, there is provided a secondcutoff portion separating the plunger chamber and the exterior of thesolenoid main body from each other, whereby it is possible to morereliably prevent contaminants from entering the plunger sliding portion.

By providing a filter in the through-hole formed in the rod, it ispossible to prevent contaminants or the like from entering the fluidaccumulating chamber.

Also, by providing at the end of the rod on the fluid accumulatingchamber side an elastic partition separating the fluid accumulatingchamber and the interior of the through-hole from each other, it ispossible to prevent contaminants or the like from entering the fluidaccumulating chamber.

1. A solenoid, characterized in that the solenoid comprises: excitationmeans provided in a solenoid main body and excited through energization;a center post secured in position inside the solenoid main body; aplunger slidably provided in a bearing portion in a plunger chamberdefined in the solenoid main body and adapted to be attracted to saidcenter post by a magnetic force through excitation of said excitationmeans; a fluid accumulating chamber provided substantially coaxiallywith said plunger chamber and on the opposite side of said center postthrough the intermediation of the plunger chamber; and a rod which isfixed to the inner periphery of a through-hole formed in said plunger,one end of which protrudes so as to reach the fluid outside the solenoidmain body through a through-hole formed in said center post, and theother end of which protrudes so as to reach the interior of said fluidaccumulating chamber, and that said rod has a through-hole for guidingthe fluid outside said solenoid main body only to the interior of saidfluid accumulating chamber, and that a first cutoff portion separatingsaid plunger chamber and the fluid accumulating chamber from each otheris provided on and is in contact with the outer peripheral side of saidrod.
 2. The solenoid according to claim 1, characterized in that saidfirst cutoff portion consists of an annular member, and the innerperiphery of the annular member is caused to slide on the outerperiphery of said rod, and, further, the outer periphery of the annularmember is brought into close contact with the inner peripheral portionof said fluid accumulating portion, whereby said plunger chamber and thefluid accumulating chamber are separated from each other.
 3. Thesolenoid according to claim 1, characterized in that the sliding portionbetween the inner periphery of said annular member and the outerperiphery of said rod is positioned outside the magnetic path formedwhen said excitation means is excited.
 4. The solenoid according toclaim 1, characterized in that a second cutoff portion is provided onthe outer peripheral side of said rod, separating said plunger chamberand the exterior of the solenoid main body from each other.
 5. Thesolenoid according to claim 1, characterized in that at least one ofsaid first and second cutoff portions is the bearing of said rod.
 6. Thesolenoid according to claim 1, characterized in that at least one ofsaid first and second cutoff portions is a seal member sealing the outerperiphery of said rod.
 7. The solenoid according to claim 1,characterized in that a filter is provided in the through-hole formed insaid rod.
 8. The solenoid according to claim 1, characterized in that anelastic partition is provided at the end of said rod on the fluidaccumulating chamber side, separating the fluid accumulating chamber andthe interior of said through-hole from each other.